Chronology of labyrinthitis ossificans induced by Streptococcus pneumoniaemeningitis

Objective: Labyrinthitis ossificans consists of novel osteogenesis that fil ls the normally patent cochlear and vestibular lumen as an end-stage sequel ae to various pathologies, This study was designed to establish the sequenc e of events and chronology of the osteoneogenesis and calcification. Study Design: A prospective randomized double-blind study. Methods: By using seri al application of different colored fluorochromes, which deposit in newly f orming bone, the timing of bone deposition and bone remodeling can be estab lished. Labyrinthitis ossificans was induced in six groups (n = 5) of gerbi ls by an intrathecal injection of live Streptococcus pneumoniae. Group 1 re ceived no fluorochrome labels, group 2 received one label, group 3 received three labels, and groups 4, 5, and 6 received four labels. The temporal bo nes were harvested after 2 weeks (group 1), 1 month (group 2), 3 months (gr oup 3), 4 months (group 4), 6 months (group, 5), and 12 months (group 6), R esults: Sixteen of the 25 animals that received labels developed ossificati on, demonstrated with fluorescent microscopy, In the animals that developed labyrinthitis ossificans, newly formed disorganized bone began calcifying as early as 3 weeks (label 1) after S pneumoniae injection. Osteoneogenesis continued as evidenced by the presence of the other labels when first appl ied at 6 weeks (label 2), and 10 weeks (label 3), Ossification, calcificati on, and remodeling proceeded through a 12-month course, wherein a reduction of labels was present at 6 months and total disappearance by 12 months. Co nclusions: The use of fluorescent stains in this animal model provides a me ans to establish a timeline of the ossification seen in labyrinthitis ossif icans.